1. Field of the Invention
The present invention relates in general to a hydrostatically releasable coupling assembly and, more particularly, to a hydrostatic release with a composite plunger assembly.
2. Description of the Prior Art
Hydrostatically releasable coupling devices such as those shown in U.S. Pat. Nos. 2,824,315 and 3,534,448 are often used with a strap or other lashing arrangement to releasably secure buoyant objects to a vessel. Should the vessel sink, the hydrostatic pressure at a particular depth will cause the coupling device to become disengaged, releasing the life raft. In general, the hydrostatically releasable coupling device includes a latching mechanism and some form of a stop which may be interposed between the components of the latching mechanism to retain the mechanism in an engaged position. A diaphragm is coupled to the stop for moving the stop into and out of alignment with the latching components. During normal use, a spring urges the diaphragm in one direction to position the stop between the latching components. In the event the vessel sinks, the hydrostatic pressure at a predetermined depth depresses the diaphragm to compress the spring and separate the stop from the latching mechanism to release the life raft or other buoyant object. The coupling device may also be manually released by depressing the stop.
The hydrostatic release must operate within the specific depth ranges prescribed by various regulatory agencies. The coupling devices must be tested before shipment and periodically during the life of the device to ensure that the hydrostatic release is functioning properly. In general, the coupling devices are tested by hydrostatically depressing the diaphragm to separate the stop from the latching components while the device is under a tensioning load as required by the regulating body. If the latching mechanism fails to operate at the prescribed depth range, the hydrostatic release may fail to meet the stringent requirements established by the regulatory agencies.
The components of most hydrostatic releases, even though formed of a metal such as stainless steel, may rust or corrode because of the essentially constant exposure of the hydrostatic release to moisture and salt. Thus, rust and corrosion may accumulate on the contacting surfaces of the stop and latching components causing them to stick in the engaged position. The force that is needed to move the stop from between the latching components increases with the formation of rust. The depth at which the hydrostatic release will operate changes with the increasing amount of hydrostatic pressure required to release the latching mechanism. Depending upon the extent of rust accumulation, the hydrostatic release may fail to meet the stringent requirements set by the regulatory agencies. The formation of rust often has a substantial effect on the operation and life the coupling devices. Substantially minimizing the accumulation of rust between the stop and the latching mechanism would improve the operation of the hydrostatic release and extend the useful life of the coupling device.